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AR# 31634

Virtex-II/Virtex-4/Virtex-5 - The DCI calibration action is NOT modeled in HSPICE I/O models

Description

In the HSPICE simulation, a temperature or supply voltage variation has no effect on the DCI controlled I/O impedance value. Jitter due to the DCI calibration circuit is not present in the electrical simulation result.

Solution

DCI adjusts the output impedance or input termination to accurately match the characteristic impedance of the transmission line. DCI actively adjusts the impedance of the I/O. This compensates for changes in I/O impedance due to process variation. It also continuously adjusts the impedance of the I/O to compensate for variations of temperature and supply voltage fluctuations.

The DCI calibration action is NOT modelled in HSPICE I/O models. For this reason if Vcco or Temperature changes in a Spice simulation and a DCI standard is used, the simulation will not give a true depiction of hardware (unless that hardware is using the "DCI Freeze" option).

The DCI calibration action can add jitter to the signal, but this will not be modelled in the HSPICE simulation.